1. Field of the Invention
The present invention relates to a non-contact type electric power supplying system for supplying electric power to an electrically powered vehicle on a non-contact basis.
2. Description of the Related Art
Electrically powered vehicles, such as transportation means such as electric train carriages and monorails, and self-guided vehicles that carry parts and so forth in factories, and so forth are known.
As one means for supplying electric power to such electrically powered vehicles, a charging station system has been implemented for electric vehicles. However, in the charging station system, whenever the electric power of the battery of the vehicle begins to run out, the user thereof should drive the vehicle to a charging station and charge it with electric power. Thus, when a parts conveying system in a factory is operated using such a charging system, the operating efficiency is low.
To solve this problem, an electric power supplying system is used. In the electric power supplying system, as in monorails, a contact-type of electric power supplying system has been proposed. However, in this system, since the contact portions get worn, they should be maintained and periodically replaced with new ones. Moreover, in the contact-type electric power supplying system, since the contact portions are subject to sparking, such a system cannot be used in an explosion-protected area.
To solve such problems, non-contact type electric power supplying systems have been proposed. FIG. 1 is a schematic diagram of a conventional non-contact type power supplying system. In FIG. 1, a guide rail 1 is disposed and supported by a rail support member 1a on a ceiling or the like. A vehicle 2 that is suspended and moved by a roller (not shown) is disposed on the guide rail 1. An electric power receiving unit 3 is disposed in the vehicle 2. The electric power receiving unit 3 is mounted on the vehicle 2 through a base portion 5 supported with a shaft 4.
FIG. 2 is a sectional view taken along lines 2--2 of FIG. 1. FIG. 2 shows a cross section of the guide rail 1 and the electric power receiving unit 3. The guide rail 1 has a bracket "!" shaped section. Two feeders 6 are disposed on a side surface of the guide rail 1 and supported by support members 7. In other words, the feeders 6 are located along the guide rail 1. The electric power receiving unit 3 has an E-shaped section. A secondary coil 9 is disposed at a center convex portion of the electric power receiving unit 3. The electric power receiving unit 3 is made of silicon steel. Each of the feeders 6 is located within the respective concave portions of the E-shaped section of the electric power receiving unit 3.
When an AC current with a predetermined frequency (for example, 10 kHz) is supplied to the feeders 6 from an AC power supply (not shown), a voltage is induced in the secondary coil 9 of the electric power receiving unit 3. In other words, when an AC current with a predetermined frequency is supplied to the feeders 6, a magnetic circuit is formed around the feeders 6 through the electric power receiving unit 3 and a part of the guide rail 1. Thus, a voltage is induced in the secondary coil 9 due to electromagnetic induction. The voltage (electric power) obtained in such manner is used to move the vehicle 2.
The voltage induced by the secondary coil 9 is obtained by an AC magnetic field that generates a high frequency current that flows in the feeders. Thus, when the distance between the feeders 6 and the electric power receiving unit 3 (for example, the distance L from an edge surface of the electric power receiving unit 3 to the feeders 6 shown in FIG. 2) varies, the induced voltage varies. When the guide rail 1 is straight, the distance between the feeders 6 and the electric power receiving unit 3 is nearly constant. Thus, the voltage induced by the secondary coil 9 does not appreciably deviate.
However, since the guide rail 1 is disposed in, for example a factory, it has a curved portion as well as a straight portion. For example, as shown in FIG. 1, as with a corner portion of a conveying system, the guide rail 1 has a curved portion. The above-described distance L deviates by +.DELTA.L or -.DELTA.L. This deviation is proportional to the length of the electric power receiving unit 3 (namely, the length B of the core of the electric power receiving unit 3 (see FIG. 1)). Thus, the induced voltage decreases corresponding to the amount of the deviation.
In other words, as shown in FIG. 1, the electric power receiving unit 3 has a predetermined length B in the moving direction of the vehicle 2. Thus, when the vehicle 2 passes through the corner portion, the relative position of the feeders 6 within the electric power receiving unit 3 is denoted by a curved feeder line 6 shown in FIG. 3. On the other hand, assuming that an optimum position in which the electric power receiving unit 3 most effectively receives electric power from the feeders 6 is in the range denoted by dashed lines shown in FIG. 4, the corner portions 3a and 3b of unit 3 as shown in FIG. 3 are not preferable for the electric power receiving unit 3 to receive electric power (the dashed lines shown in FIG. 3 correspond to the optimum position shown in FIG. 4). Thus, a leakage flux or the like increases and thereby sufficient electric power cannot be supplied to the vehicle 2.